Stable isotope on the evaluation of water quality in the presence of WWTPs in rivers.

We investigated the distribution of nitrogen compounds in Han River as well as two tributaries of Tancheon and Jungrangcheon. Particularly, we observed the significant releases of NH -N from effluent of wastewater treatment plants (WWTPs) in two tributaries that has resulted in the increases of ammonium nitrogen (NH -N) in Han River as well as in Tancheon and Jungrangcheon. Due to the increases of NH -N in two tributaries, the larger distribution of δN-NH was observed than those of δN-NO in downstream. We calculated the contribution rate of ammonium nitrogen and nitrate nitrogen from effluent to downstream according to the results of stable isotope. The contribution rates of δN-NH from effluent to downstream were significant that ranged between 53 and 100 % in Tancheon and between 27 and 100 % in Jungrangcheon. While the contribution of δN-NO was not significant in Tancheon, it was occasionally observed in Jungrangcheon. These results demonstrated that WWTPs are the major sources of NH -N in two tributaries, which caused the distinguishable stable isotope of δN-NH . Therefore, the stable isotope of δN-NH could be a useful parameter or tracer for the evaluation of NH-N released from WWTPs in rivers. [ABSTRACT FROM AUTHOR]